Background: Every day, 30,000 to 40,000 ICU patients in the United States are suffering from acute brain dysfunction called delirium. This problem is getting larger every year due to the aging of our population. Delirium is a serious acute medical condition. It has been called a medical emergency. A delirium is a serious, high-frequency complication in intensive care unit (ICU) patients. (Incidence: 40–82%) being defined as a transient organic mental syndrome characterised by a disturbance in awareness, cognition and attention. The aim of this study was a review of the international bibliography in the subject of delirium in ICU. Method and Material: The method of this study included bibliography research from both the review and the research literature. The search was performed using the following key terms: ICU, psychosis, delirium, mortality Results: The nurses should be aware of all the procedures, which reduce the probabilities of the patients , making vulnerable to life delirium. The understanding of the status of the patient with delirium syndrome and the synthesis of all the available data may lead to a global approach and to a proper treatment. It is important for the nurses to learn the tools to stratify the severity of delirium. Conclusions: If tools to stratify the severity of delirium were available, nurses could be better able to "recognize patients who are at the highest risk for negative outcomes". This would enable prevention and early treatment of delirium, avoiding debilitating after-effects in patients and unnecessary strains on hospital resources. The findings of the research reveal that "should stimulate future research in the field of delirium prevention and treatment".